Refractory article and furnace lining made therefrom



Patented 3m. 13, 1931 UNITED STATES PATENT OFFICE,

RAYMOND c. IBENNEB AND GEORGE J. EASTER, or NIAGARA frALLs, rinw Your.

ASSIGNORS no man CARBORUNDUM comrm, or NIAGARA FALLS, NEW YORK, A

CORPORATION OF PENNSYLVANIA REFRACTORY ARTICLE AND FURNACE LINING MADETHE REFROH No Drawing.

dize or decompose under the influence of furnace gases, and a method formaking same. We refer particularly to refractories containing graphite,carbon, silicon carbide, etc.

The object of our invention is to provide refractory articles, which,while made from the same substances as in the past, offer greaterresistance to the penetration of furnace gases, particularly at hightemperatures and hence do not deteriorate so rapidly.

It is evident that within the limits of the speed of the reactionbetween the furnace gas or slag and the active constituent of therefractory, the life of the refractory is dependent upon the number andsize of the permeable pores, as they permit the penetration of slags andgases, which accelerate the 'destruction of the article. I

It'is recognized in the art that the permeability of a refractory brickmay be decreased in two ways. The first consists in closing the pores ofthe bricks by various means, such as those described in U. S. Patent#1,472,386,

to E. B. Forse. This relief is, however, only..-

temporary and is lost as soon as the original facing glaze of the bricksis destroyed to even the entire article.

a slight extent. The second way comprises the use of mulled grain, i.e., grain from which.

the sharp corners have been removed, so that better packing of particlesis achieved with consequentreduction in porosity throughout This methodis described in copending application of F. J. Tone, Serial No. 455,716,filed May 26" 1930, for an improvement in low permeable refractory andmethod of making the same.

We have discovered that in spite of these precautions there is amarkedpermeability in bricks as ordinarily made, particularly in thedirection perpendicular to that in which ressure is applied informingthepiece. or instance, we have observed the Application filed April 6,

1927; Serial No. 181,602.

followin 'in representative cominercially made re actories (measurementsbeing as described below) r For measuring the permeabilities above, we

the brick and allow it to escape only at the opposite face (the othersbeing sealed by immersion in mercury). The air flow through the specimenis then measured by -a meter in the air line ahead of the brick. Inorder to compare the value of air flow in one direction with that in theother, it is 'of course necessary to reduce the values to a commonbasis. sult is secured by multiplying theobserved flow by the thicknessand dividing the product by the area and pressure. In this way thepermeability is expressed in terms of air flow through a unit cube underunit pressure.

The difiernce in permeability in difier- We have found that the desiredreent directions is due to a sort of lamination of the brick. In cut andpolished microscopic specimens this lamination is often discernible,particularly in used brick which bination of permanent and temporarybonds,

the plasticity being supplied by the bonds and water. The grains. are ofirregular apply air at a known pressure to one face of 5 a pressure isapplied, i. e., the brick becomes.

degree, having layers shapes and include many comparatively broad thinpieces. As pressure is applied to these irregular pieces they musteither resist it rigidly or twist until they assume a positionpresenting a broad surface to resist the pressure (the situation beinganalogous to their arrangement if each were placed on a plate andallowed to come to rest under the influence of gravity). Of course mostof them twist, displacing the more plastic bond material from their pathand forcing it to flow into positions where there is the minimumpressure on it. In this way a relatively large proportion of broad flatfaces become completely or partly perpendicular to the pressure and thecorresponding narrow edges are parallel to the pressed face.

This results in the crystals approaching one another more-closely attheir sides than in the direction parallel to that in which stratifiedto a certai in which crystals predominate'separated by layers in whichbond predominates. Upon burning, the temporary bond is removed and thepermanent bond usually shrinks slightly, thus leaving open pores.between grains. Since the bond occurs in strata it is only natural thatthe pores should thus be stratified also and greater permeabilityperpendicular to the direction of pressure results. A

, Heretofore this factor has not been known and brick are commonlypressed on the broad face. This makes the laminations parallel to thebroad face and leaves the spaces between them open to entrance fromtheside or end of the brick which for reasons of structural stability ispractically al ways the face exposed in the furnace. Thus the brick isplaced so as to offer the greatest opportunity for its destruction byentrance of. slag or oxidizing gases.

Having thus described the underlying I phenomena of our invention andthe method of measuring the factors involved, our invention consists inpressing the block in such manner that the minimum permeability is in adirection perpendicular to that face of the block which is exposed inthe furnace wall. This may be attained by pressing the piece from theface in question during the in the case of thic er ware, by pressingfrom both that face and the opposite one.

The blocks are then laid in the furnace lining so that the exposedface-isa face which has been subjected to direct pressure in the formingof the blocks. A furnace lining formed in this'way has apermeability'in: a direction parallel to the opposite faces of greatestarea and perpendicular to. the longitudinal axis of theblocks of whichit is composed, which'is less than.'75% of ular to the exposed pfocessof manufacture, or

of the other faces.

the permeability in directions at right an gles thereto. y r

In this way advantage is taken of the structural nature of the blocks togive minimum permeability to the exposed surface of the furnace lining.This is of particular importance in a lining which is of an oxidizablenature, such as one formed at least wholly or in part of silicon carbideand a bonding agent.

We claim: a l I A 1. A furnace lining comprised of refractory blockswhich have been pressed in"a direction perpendicular to the plane of theexposed faces of the blocks.

2. vA, method of making furnace linings which consists in moulding andpressing refractory mass into a block with the pressure applied in adirection at right angles to the surface of the block adapted to'beexposed, then laying the blocks so that the'exposed faces of the blocksare perpendicular tosurfaces of the blocks which have been subjected todirect pressure' 3. A furnace lining comprised of refractory blockswhich have the lowest permeability in a direction perpendicular to theexposed faces of the blocks.

4; A furnace lining comprised of refractory blocks havingaermeabilityerpendic- V faces of the locks less than ;0% of the permeabilityparallel to said faces.

I 5. A furnace lining comprising refractory blocks having a permeabilityperpendicular use to the exposed. face thereof lower than the Ipermeabilityin a direction parallel to the exposed face and made atleast in part of silicon carbide. c

6. A furnace lining comprised of refractory blocks having a permeabilityperpendicular to their exposed surfaces less than 7 5.0%?

of their permeability in a direction arallel to their exposed faces andmade at east in part of sicilon carbide.

7 A furnace lining madeat least in part from blocks of an oxidizablematerial and having a permeability perpendicular to the exposed facesthereof lower than that in the direction parallel to said exposed faces.

8. A refractory wall made at least in part from blocks of an oxidizablematerial, said blocks having a permeability perpendicular to the exposedfaces thereof less than 75.0% of-the permeability parallel to thesaid-exposed faces.

- -9. A refractory article composed of bonded grains and having theshape of a brick occursin which the minimum permeability in a directionparallel to the opposite faces of greatest area and perpendicular to.one

10. A refractory article composed of bonded grains of an oxidizablematerial and hav- 7 ing the Shape of a r k in which t hemini mumpermeability occurs in a direction parallel to the opposite faces ofgreatest area and perpendicular to one of the other faces.

11. A refractory article composed of bonded grains of an oxidizablematerial and having the shape of a brick in which the permeability in adirection parallel to the opposite faces of greatest area andperpendicular to one of the other faces is less than 75% of thepermeability in either of the mutually perpendicular directions.

12. A refractory article composed of bonded silicon carbide grains andhaving the shape of a brick in which the permeability in a directionparallel to the opposite faces of greatest area and perpendicular to oneof the other faces is less than 75% of the permeability in either of themutually perpendicular directions.

In testimony whereof we have hereunto set our hands.

' RAYMOND C. BENNER. GEORGE J. EASTER.

